The present invention relates to an electrophotographic image forming apparatus, and a process cartridge.
Here, an electrophotographic image forming apparatus includes, for example, an electrophoto-graphic copying machine, an electrophotographic printer (for example, LED printer, laser beam printer, and the like), an electrophotographic facsimile apparatus, an electrophotographic word processor, and the like.
A process cartridge means a cartridge in which a charging means, a minimum of one processing means, either a developing means and a cleaning means, and an electrophotographic photosensitive member, are integrally placed, and which is removably mountable in the main assembly of an electrophotographic image forming apparatus; or a cartridge in which a minimum of a developing means, and an electrophotographic photosensitive member, are integrally placed, and which is removably mountable in the main assembly of an image forming apparatus.
Conventionally, an image forming apparatus which employs an electrophotographic image formation process also employs a process cartridge system. According to a process cartridge system, an electrophotographic photosensitive member, and a single or plural processing means, which act on an electrophotographic photosensitive member, are integrally placed in a cartridge which is removably mountable in the main assembly of an image forming apparatus. Also according to this process cartridge system, an image forming apparatus can be maintained by users themselves without relying on service personnel, and therefore, operational efficiency can be drastically improved. As a result, a process cartridge system is widely used in the field of the image forming apparatus.
In the case of an electrophotographic image forming apparatus employing such a process cartridge system as described above, users themselves replace a process cartridge. Thus, some image forming apparatuses or process cartridges are provided with a means for informing the users of the remaining amount of developer as developer is consumed.
As for a conventional apparatus for detecting the remaining amount of developer, a set of two electrically conductive rods are placed in a developer container, and the change in the electrostatic capacity between the two rods is detected to estimate the amount of the developer in the container.
Japanese Laid-Open Patent Application 5-100571 discloses a developer amount detecting apparatus which employs a developer amount detecting member comprising a more sophisticated pair of electrodes than the aforementioned pair of electrically conductive rods. More specifically, it comprises a pair of thin flat electrodes which look like the head portion of a rake with parallel tines, and are placed adjacent to each other in such a manner that the parallel tines of one electrode fit in the intervals of the parallel tines of the other electrode, one for one, forming a labyrinth between the two electrodes. This developer amount detecting member is placed on the bottom surface of the developer chamber of the developer container. In the case of this developer amount detecting apparatus, the change in the amount of the electrostatic capacity between the two electrodes, the parallel tines of one of which are placed in parallel to the parallel tines of the other in the same plane, is detected to determine the remaining amount of the developer.
However, in both of the above described developer amount detecting apparatuses, what is detected is whether or not developer is present in the developer container; in other words, what the above developer amount detecting apparatuses can detect is that the amount of the developer in the developer container is small immediately before the developer container runs out of the developer. Therefore, they cannot determine the amount of the developer remaining in the developer container.
In comparison, if it is possible to substantially continuously (or substantially real time) detect the amount of the developer remaining in the developer container, a user can estimate when the current process cartridge needs to be replaced, based on the remaining amount of the developer in the developer container, and can prepare a fresh process cartridge accordingly. This is very convenient for the user.
The primary object of the present invention is to provide a process cartridge, and an electrophotographic image forming apparatus, the remaining amount of the developer in which can be substantially continuously (or substantially real time) detected.
Another object of the present invention is to provide a process cartridge and an electrophotographic image forming apparatus, the remaining amount of the developer in which can be continuously detected on the basis of the change in electrostatic capacity.
Another object of the present invention is to provide a process cartridge and an electrophotographic image forming apparatus, the remaining amount of the developer in which can be continuously detected more accurately, compared to a conventional process cartridge and a conventional electrophotographic image forming apparatus.
Another object of the present invention is to provide a process cartridge and an electrophotographic image forming apparatus, in which the developer does not adhere to the surface of the developer amount detecting member, and/or the surface of the cartridge frame, and the remaining amount of the developer in which can be continuously detected.
Another object of the present invention is to provide a process cartridge and an electrophotographic image forming apparatus, the remaining amount of the developer in which can be continuously detected with the use of a developer amount detecting member placed on the external surface of the cartridge frame.
Another object of the present invention is to provide a process cartridge and an electrophotographic image forming apparatus, which comprise a developer amount detecting member placed on the external surface of the cartridge frame, and in which the portion of the internal surface of the process cartridge frame, the position of which corresponds to the position of the developer amount detecting member on the external surface of the cartridge frame, can be wiped by a developer conveying member.
Another object of the present invention is to provide a process cartridge and an electrophotographic image forming apparatus, which comprise a developer amount detecting member for generating electrical signals used by the main apparatus of the image forming apparatus to continuously detect the remaining amount of the developer, and in which the developer amount detecting member is attached to the cartridge frame, across the portion which is given a cylindrical curvature, and is wiped by the developer conveying member as the developer conveying member is rotated, in a manner to conform to the surface of the portion to which it is attached, along the passage of the developer from the developer container to the developing member.
These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.